Purpose

This study aims to numerically study the buoyant convective flow of two different nanofluids in a porous annular domain. A uniformly heated inner cylinder, cooled outer cylindrical boundary and adiabatic horizontal surfaces are considered because of many industrial applications of this geometry. The analysis also addresses the comparative study of different porous media models governing fluid flow and heat transport.

Design/methodology/approach

The finite difference method has been used in the current simulation work to obtain the numerical solution of coupled partial differential equations. In particular, the alternating direction implicit method is used for solving transient equations, and the successive line over relaxation iterative method is used to solve time-independent equation by choosing an optimum value for relaxation parameter. Simpson’s rule is adopted to estimate average Nusselt number involving numerical integration. Various grid sensitivity checks have been performed to assess the sufficiency of grid size to obtain accurate results. In this analysis, a general porous media model has been considered, and a comparative study between three different models has been investigated.

Findings

Numerical simulations are performed for different combinations of the control parameters and interesting results are obtained. It has been found that the an increase in Darcy and Rayleigh numbers enhances the thermal transport rate and strengthens the nanofluid movement in porous annulus. Also, higher flow circulation rate and thermal transport has been detected for Darcy model as compared to non-Darcy models. Thermal mixing could be enhanced by considering a non-Darcy model.

Research limitations/implications

The present results could be effectively used in many practical applications under the limiting conditions of two-dimensionality and axi-symmetry conditions. The only drawback of the current study is it does not include the three-dimensional effects.

Practical implications

The results could be used as a first-hand information for the design of any thermal systems. This will help the design engineer to have fewer trial-and-run cases for the new design.

Originality/value

A pioneering numerical investigation on the buoyant convective flow of two different nanofluids in an annular porous domain has been carried out by using a general Darcy–Brinkman–Forchheimer model to govern fluid flow in porous matrix. The results obtained from current investigation are novel and original, with numerous practical applications of nanofluid saturated porous annular enclosure in the modern industry.

中文翻译：

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纳米流体在垂直多孔环空中的浮力传热：不同模型的比较研究

目的

本研究旨在数值研究多孔环形域中两种不同纳米流体的浮力对流。由于这种几何形状的许多工业应用，考虑了均匀加热的内圆柱、冷却的外圆柱边界和绝热水平表面。该分析还涉及对控制流体流动和热传输的不同多孔介质模型的比较研究。

设计/方法/途径

有限差分法已被用于当前的模拟工作中以获得耦合偏微分方程的数值解。具体地，交替方向隐式方法用于求解瞬态方程，连续线过松弛迭代法通过选择松弛参数的最佳值来求解时间无关方程。采用辛普森规则估计涉及数值积分的平均努塞尔数。已执行各种网格灵敏度检查以评估网格大小是否足以获得准确结果。在此分析中，考虑了一般的多孔介质模型，并研究了三种不同模型之间的比较研究。

发现

对控制参数的不同组合进行了数值模拟，并获得了有趣的结果。已经发现，达西数和瑞利数的增加提高了热传输速率并加强了多孔环空中的纳米流体运动。此外，与非达西模型相比，达西模型检测到更高的流动循环率和热传输。可以通过考虑非达西模型来增强热混合。

研究局限性/影响

在二维和轴对称条件的限制条件下，目前的结果可以有效地用于许多实际应用。当前研究的唯一缺点是它不包括三维效应。

实际影响

结果可用作任何热系统设计的第一手资料。这将有助于设计工程师减少新设计的试运行案例。

原创性/价值

通过使用通用 Darcy-Brinkman-Forchheimer 模型控制多孔基质中的流体流动，对环形多孔域中两种不同纳米流体的浮力对流流动进行了开创性的数值研究。从目前的调查中获得的结果是新颖的和原创的，在现代工业中纳米流体饱和多孔环形外壳有许多实际应用。